The existing communication system involves different methods of Multiple Access, for example, Code Division Multiple Access (CDMA) and Interleave Division Multiple Access (IDMA). The CDMA means that different users use different spread code sequences to transmit information, and the IDMA means that different users use different interleavers to transmit information.
In the CDMA technology, the Forward Error Correction (FEC) is concatenated with spreading operation on the transmitter side. From the perspective of the channel coding theory, the spreading operation does not obtain any coding gain, and the IDMA technology substitutes low bit rate FEC for the concatenation between the FEC and the spreading operation in the CDMA technology. Therefore, the coding gain can be maximized. In both theory and practice, it is proved that the IDMA technology provides higher spectrum utilization ratio compared with the CDMA technology.
In the prior art, the IDMA-based data transmission solution employs binary codes. For details, see FIG. 1 and FIG. 2.
FIG. 1 shows an IDMA transmitter apparatus under high-order modulation in the prior art. The apparatus includes a binary encoder 101, a spreader 102, an interleaver 103, and a symbol mapper 104. The detailed process is as follows:
The user source data frame is processed by the binary encoder 101 into an encoded sequence, the encoded sequence is processed by the spreader 102 into a spreading sequence, the spreading sequence is processed by the interleaver 103 into an interleaved sequence, and the interleaved sequence is processed by the symbol mapper 104 into a symbol sequence, which is then sent out.
FIG. 2 shows an IDMA receiver apparatus under high-order modulation in the prior art. The apparatus includes a multi-user demodulator 201, a symbol-bit probability converting unit 202, a de-interleaver 203, a de-spreader 204, a binary decoder 205, a spreader 206, an interleaver 207, and a bit-symbol probability converting unit 208. The detailed process is as follows:
In the forward link, the multi-user demodulator 201 calculates the symbol posteriori probability information for the received symbol sequence. The symbol posteriori probability information is processed by the symbol-bit probability converting unit 202 into bit posteriori probability information, and the bit posteriori probability information is processed by the de-interleaver 203 and the de-spreader 204, and then input to the binary decoder 205 for decoding.
In the reverse link, the binary decoder 205 outputs the bit priori probability information of the encoded sequence to the spreader 206. The spread bit priori probability information after being spread by the spreader 206 passes through the interleaver 207, and is input to the bit-symbol probability converting unit 208. The bit priori probability information is converted into symbol priori probability information, which is sent to the multi-user demodulator 201 again for the next iterative operation until the preset maximum iterative count is met.
The prior art reveals that: First, binary codes are used for data transmission in the prior art, but the binary codes are not much capable of error correction or resisting burst errors; second, in the transmitter solution in the prior art, after passing through the spreader and the interleaver, the encoded bit data is mapped to symbol data for sending. Because the number of data units of the bit data is greater than the number of data units of the symbol data, the spreader and the interleaver need to perform plenty of operations, thus leading to much complexity of operation in the prior art.
Further, in the receiver solution in the prior art, the data is transmitted in the binary code mode, namely, the binary decoder can identify only the bit probability information. Therefore, the receiver needs to convert the symbol probability information into bit probability information after receiving the symbol sequence and calculating out the symbol probability information of the symbol sequence, and then the information can be referred to the binary decoder. Likewise, the binary decoder outputs bit probability information, which needs iteration, and the bit probability information needs to be converted into symbol probability information. Therefore, in the case of high-order modulation, the receiver needs to perform frequent conversion between the symbol probability information and the bit probability information, thus leading to much complexity of operation.
Further still, in the conversion between the symbol probability information and the bit probability information, information may be lost, the coding gain is partially lost, and the system performance is affected.